#29641: Add support for unique constraints to Meta.constraints
-------------------------------------+-------------------------------------
Reporter: Simon | Owner: Simon Charette
Charette |
Type: New | Status: assigned
feature |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Just like `Meta.indexes[Index]` allows more granularity over
`Field.db_index=True`/ `Meta.index_together` we should make
`Meta.constraints[UniqueConstraint]` an analog for
`Field.unique=True`/`Meta.unique_together`.
This ticket proposes to introduce
`django.db.constraint.UniqueConstraint(fields, name)` to allow such
constraints to be defined with the sole extra feature of allowing a `name`
to be specified.
The mid-term goal of this feature addition is to rely on the partial
indices work (#29547) that is likely to land in 2.2 to allow partial
unique constraints to be defined which is a really useful feature.
e.g.
{{{#!python
class Tweet(models.Model):
user = models.ForeignKey(User, models.CASCADE)
pinned = models.BooleanField(default=False)
class Meta:
constraints = [
UniqueConstraint(
fields=['user', 'pinned'],
condition=Q(pinned=True),
name='pinned_tweet'
),
]
}}}
Adding support for partial constraints should be tracked in a future
ticket as this one will focus on refactoring the `CheckConstraint` work
added for #11964 to the definition of different type of constraints.
--
Ticket URL: <https://code.djangoproject.com/ticket/29641>
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